From a very young age, Boris Stavrovski understood that specificity is the key to a meaningful collection. As a boy of only 16, he started amassing medieval Russian coins, becoming the chairman of Moscow’s premier coin club in college. By the time he was 30, his collection had grown so valuable that it was purchased by the Hermitage. “If you are collecting everything, you may not be able to collect anything,” he says.But if this motto implies moderation, it is misleading. The walls of Stavrovski’s modest two-bedroom apartment on New York’s Upper East Side are so jammed with paintings by early 20th-century Russian artists that the resulting horror vacui might spark alarm about their stability. However, Stavrovski, a 62-year-old computer science professor at the City University of New York, worked together with a contractor on a steel exoskeleton that braces the apartment. The pictures, surrounded by spectacularly ornate Renaissance, Baroque and Art Deco frames, can hang plentifully and heavily without bringing down the drywall.The remarkable paintings, drawings and sculptures that crowd Stavrovski’s home are only a taste of his nearly 400-work collection, which consists mostly of pieces by artists who collaborated with legendary Ballets Russes director Sergey Diaghilev. Stavrovski began collecting artists like Natalia Goncharova, Mikhail Larionov, George Annenkov and Alexander Benoiswho all designed costumes and sets for Diaghilev’s Paris-based company—in 1994, three years after he emigrated to the United States. His passion is rooted in their artistic achievement but also derives from their status as fellow Russian émigrés.